Retail games will be for any DS, but the DSi will have DSiWare, like the Wii has WiiWare. It's possible that Nintendo will release retail DSi only games, but games like Mario and Luigi 3 will be for every DS.

The camera just seems like a Gameboy Camera V2 to me, really, its like deja vu with that. Personally I think the camera addition is stupid...but we'll see if its cool, hopefully Nintendo can find some way to convince me.